1. Field of the Invention
The present invention relates to a variable capacitor having variable capacitance according to a control signal and an integrated circuit (IC) including the variable capacitor.
2. Description of the Related Art
As a recently wireless communications technology has been developed, 4G mobile communications, supporting long term evolution (LTE) has been prominent in addition to the current 3G mobile communications technology.
As 4G mobile communications networking is added to existing 3G mobile communications networking, there is an increase in communications techniques supported in a single mobile communications terminal.
Accordingly, a radio frequency (RF) function of a mobile communications terminal needs to cover various frequency bands by using a single RF chain, and needs to optimize front-end matching including an antenna and power consumed by a power amplifier (PA) while the mobile communications terminal is being used.
To implement such an RF function, a tunable matching circuit block is added to an existing front-end circuit. In this regard, a variable device may be used to perform a variable function, and accordingly, a variable capacitor is used.
The variable capacitor may include capacitors utilizing various techniques. Among these techniques, research into a metal-insulator-metal (MIM) technique using a CMOS process that is advantageous in terms of manufacturing costs has been actively conducted. An MIM capacitor may operate in connection with an MOS switch owing to its characteristics.
Such a MIM capacitor applies a digital control signal to a switch without an additional DAC and controls capacitance. As described in the related art document below, important parameters in the variable capacitor are a Q value that is a quality factor and a tuning range. To possess certain RF performance, the Q value must be maintained.